1. Field of the Invention
The present invention relates to data transmission technologies, and more particularly, to an apparatus and method for checking validity of an 8B/10B code-group.
2. Description of the Related Art
Many of recent high-speed telecommunications systems in addition to the gigabit Ethernet, have employed DC-Balanced 8B/10B line code technologies standardized as a binary line coding method in ANSI X3.230-1994(FC-PN). The reason why the DC-Balanced 8B/10B line code technologies are used is because design of a transmitter and receiver for that is not complicated and immunity of the system against noise on lines can be improved without spending much cost.
In a data transmission method using the 8B/10B line code, the transmission side converts an 8-bit data into a 10-bit data according to a predetermined rule and transmits the data serially over transmission lines, and the reception side aligns the serially received data in a 10-bit data and again converts into an 8-bit data according to a predetermined rule. In the telecommunications technology field such as gigabit Ethernet, a 10-bit data generated by a predetermined rule is referred to as a code-group. Hereinafter, a code group in the present invention is referred to as an 8B/10B code-group.
In the prior art running disparity detection methods, there is a method using a nibble clock and a bit clock. This method needs double jobs, in which the boundary of an 8B/10B code-group is found and serial-to-parallel converted data are again converted into serial data, and also needs an additional apparatus for generating nibble clocks.
In another prior art running disparity detection method, the number of ones in the 10-bit data of a previously received 8B/10B code-group is obtained based on a currently received 8B/10B code-group, and the number of ones in the most significant 4-bit nibble is obtained again, and by using these two numbers, the previous running disparity is obtained. Then, the number of ones in the least significant 6-bit nibble of the currently received 8B/10B code-group and the number of ones in the most significant 4-bit nibble of the currently received 8B/10B code-group is obtained, respectively. Then, by using these three values, the previous running disparity, the disparities of the least significant 6-bit nibble and the most significant 4-bit nibble in the currently received 8B/10B code-group, the current running disparity is obtained.
Compared to the first prior art, the second prior art is not simpler in implementation and the execution time is not shortened.
Thus, when the prior art 8B/10B code-group validity detection apparatus is employed in a high-speed system such as a gigabit system, a critical path, which indicates the number of combinational logic circuits that should be operated in a unit time, is relatively long such that violation of a processing time limit may occur.